Known ink metering systems regulate the film of ink by means of a duct blade or an ink spreader using an immersed or film roller. For example, East German Patent Specification No. 104 259 discloses a metering system with nip regulation accomplished by simultaneous variation of the differential speed between the duct roller and the squeegee roller. For reasons of space, the metering discs are suspended only on one side and the transverse spreading movement tends to buckle the mounting plate during operation. Also, the differential speed between the duct roller and the ink-taking roller results in additional forces on the disc mountings.
West German Patent No. 2 210 020 also discloses an inking unit in which the metering and transfer rollers are mounted to be relatively movable, a plurality of bimetallic strip spring assemblies being provided which act on the metering roller side remote from the transfer roller. The object of this system is to obtain a specific spacing between the rollers even in the event of temperature fluctuations, and thus obtain a film of ink of constant thickness on the applicator roller.
The disadvantage of each of these known ink metering systems is that the ink is fed from an ink bath, i.e., they have relatively considerable amounts of dead ink which tends to form a skin unless ink agitating means are used. Another disadvantage is that the ink readily becomes dirty and its water content increases. Cleaning the ink bath results in a relatively high ink loss and if this is to be avoided the printer must keep an accurate check as the run is completed, so that the amount of ink required for any other sheets to be printed is still available in the ink duct.